1. Field of the Invention
The present invention relates to an upright piano type action which includes an action for an upright piano and an action of the same type as the action for an upright piano.
2. Description of the Related Art
A conventional action of an upright piano is designed, in order to allow a hammer to hit a string, such that a jack which operates in response to a depression of a key pushes up a surface of a butt to make the hammer supported by the butt swing (e.g., Japanese examined utility model publication No. 62-43349).
Hereafter, the direction in which the hammer (or a swinging member) swinging back and forth moves when a key is depressed is referred to as forward, whereas the direction in which the hammer moves when the key is released is referred to as backward.
The butt, which has a butt main body formed of a plate member supported via a butt flange by a center rail so that the butt can swing, is designed such that a back surface of the butt is pushed up by the jack to swing. The surface which the jack pushes is covered with a butt skin. Between the butt main body and the butt skin, an under cloth and an under felt are sandwiched such that the under cloth and the under felt are arranged in the direction in which the butt is pushed up as described below.
In a state where the key is not depressed, more specifically, the lower end surface of the butt is horizontal or slightly descends backward. On the lower end surface, the under cloth is adhered. The butt also has an inclined surface which extends from the back end of the lower end surface to ascend backward. On the inclined surface, the under felt is adhered. The inclined surface is connected to an upper surface which is not covered with the under felt. The upper surface extends over a step which is equivalent to the thickness of the under felt so that the upper surface connects almost smoothly to the surface of the under felt. The butt skin covers the under cloth and the under felt, being directly adhered to the upper surface.
The jack, which is supported via a jack flange by a wippen so that the jack can swing, is lifted along with the wippen in response to a depression of the key. At a position where the jack has been lifted to some extent, a jack's protruding portion placed backward comes into contact with a regulating button, so that the jack starts swinging backward to rise to the neighborhood of the utmost point to allow an escapement mechanism of the hammer to work. By the contact with the regulating button, more specifically, the jack starts swinging backward, so that the jack moves away from the butt with a tip of the jack being in contact with the butt. By such move of the jack, the jack abruptly reduces the strength by which the jack pushes up the butt. As a result, the resistance to the key-depression perceived by a player sharply reduces to allow the player realize the sense of escapement. Furthermore, when the jack swings backward to enter the neighborhood of the utmost point, the jack loses the function of pushing up the butt. As a result, the escapement mechanism of the hammer acts. Only by an inertial force, in other words, the hammer swings to a point at which the hammer hits the string. Because of the escapement mechanism, the hammer is able to return backward by use of the reaction force produced by the hitting of the string.
The butt is designed to allow the jack to act in such a manner. The area where the under cloth is adhered on the butt corresponds to an area where the tip of the jack is in contact since the jack has been lifted by the depression of the key until the contact with the regulating button. The area where the under felt is adhered corresponds to an area where the jack operates to lose the function of pushing up performed by the tip of the jack after the jack comes into contact with the regulating button to start swinging. In the area where the butt skin is adhered directly to the butt main body, the tip of the jack which no longer has the function of pushing up the butt is in contact with the butt.
Such a configuration of the butt acts as follows. Because the under cloth is provided in the area which comes into contact with the jack immediately after the start of the lifting of the jack, the under cloth serves as a cushion against the contact with the jack. The under felt makes it easy for the tip of the jack to dig into the butt because of the flexibility of the felt. By ascending in the state where the tip of the jack digs into the under felt, the jack performs the function of pushing up the butt. As a result, if the player slightly returns the key from the full stroke position to depress the key in a state where the tip of the jack has descended to the central part of the area where the under felt is adhered, the jack is able to push up the butt. Therefore, the action having such a configuration allows iterated depressions of the key at positions where the key has returned to some extent from the full stroke position. The area where the butt skin is adhered directly to the butt serves to reduce friction resistance between the jack and the butt when the key-depression has developed to the neighborhood of the full stroke position. When the jack reaches this area, the jack smoothly escapes from the butt, resulting in favorable touch perceived by the player at the time of key-depression. In the upper part of the area where the under felt is adhered and in the area where the butt skin is directly adhered, however, the jack will not perform the function of pushing up the butt even if the jack repeatedly moves up and down.